Medical treatment of several illnesses requires continuous drug infusion into various body compartments, such as subcutaneous and intra-venous injections. Diabetes mellitus patients, for example, require administration of varying amounts of insulin throughout the day to control their blood glucose levels. In recent years, ambulatory portable insulin infusion pumps have emerged as a superior alternative to multiple daily syringe injections of insulin. These pumps, which deliver insulin at a continuous basal rate as well as in bolus volumes, were developed to liberate patients from repeated self-administered injections, and allow them to maintain a near-normal daily routine. Both basal and bolus volumes must be delivered in precise doses, according to individual prescription, since an overdose or under-dose of insulin could be fatal.
A first generation of portable infusion pumps refers to “pager-like” devices with a reservoir contained within the device's housing. In the first generation devices, a long tube delivers insulin from the pump, which is attached to a belt on the patient, to a remote insertion site. Such devices are disclosed, for example, in U.S. Pat. Nos. 3,771,694, 4,657,486 and 4,498,843. These devices represent a significant improvement over multiple daily injections, but nevertheless, they all suffer from several major drawbacks, among which are the large size and weight of the device, long tubing and lack of discreetness.
To avoid consequences associated with employing a long delivery tube, a new concept was proposed, which was implemented in second generation pumps. The second generation pumps concept relates to a remote controlled skin adherable device with a housing having a bottom surface adapted for contact with the patient's skin, a reservoir disposed within the housing, and an injection needle adapted for communication with the reservoir. This paradigm was described, for example, in U.S. Pat. Nos. 5,957,895, 6,589,229, 6,740,059, 6,723,072 and 6,485,461. The second generation devices also have several limitations: they are bulky, the remote control unit should always be at hand, and they are expensive because the entire device should be discarded every 2-3 days.
Third generation skin adherable devices were devised to avoid the cost issues of the second generation devices and to extend patient customization. An example of such a device was described in the co-owned, co-pending U.S. patent application Ser. No. 11/397,115 and co-owned International Application No. PCT/IL06/001276, the disclosures of which are incorporated herein by reference in their entireties. The third generation devices contain a remote control unit and a skin adherable patch unit (also referred to as a “dispensing patch unit”) that includes two parts: (1) a reusable part containing driving and pumping mechanisms, electronics and other relatively expensive components, and (2) a disposable part containing a reservoir and, in some embodiments, batteries. A tube can also be provided which delivers the fluid from the reservoir to an outlet port that contains a connecting lumen.
This concept can provide a cost-effective skin adherable infusion device and allow diverse usage of the device, such as using it with various reservoir sizes, various needle and cannula types, etc.
In the co-pending, co-owned U.S. patent application Ser. No. 12/004,837, and co-owned International Patent Application No. PCT/IL07/001,578, both filed Dec. 20, 2007, and both claiming priority to U.S. Provisional Patent Application No. 60/876,679, filed Dec. 22, 2006, the disclosures of which are incorporated herein by reference in their entireties, a fourth generation patch unit that can be disconnected from and reconnected to a skin adherable cradle unit was disclosed. In the fourth generation the patch unit, after reservoir filling, is mounted on the body by the following steps:                1) Cradle unit is adhered to the skin;        2) Cannula is inserted through a cradle unit passageway (also referred to as a “well”) into the subcutaneous tissue. The cannula, including a rubber septum, can be connected to the cradle unit's “well”;        3) The patch unit is connected to the cradle unit. The connecting lumen pierces a rubber septum allowing fluid communication between the reservoir, cannula and the body.        
In the co-pending, co-owned U.S. patent application Ser. No. 11/706,606, the disclosure of which is incorporated herein by reference in its entirety, a device containing a dispensing patch unit (called also “insulin dispensing patch”) and an analyte sensing means (i.e., continuous glucose monitor) was disclosed. This dual function device is configured to have similar configuration to the one outlined above and can also be disconnected from and reconnected to a cradle unit upon patient discretion.
In some conventional systems, although basal delivery should be continuously administered, it is often interrupted due to periodic pump disconnection. In some situations, pump disconnection is mandatory, for example during sauna and hot bath because insulin cannot tolerate high temperatures. However, there are occasions in which a short time disconnection can substantially improve daily activity and patient satisfaction. If the operation of the patch unit's driving mechanism is not suspended prior to disconnection (for example, the user forgets to do so, the disconnection is unintentional, etc.), the patch unit will continue to dispense insulin even though it is not connected to the cradle unit, thus wasting precious insulin and battery power. Moreover, the patient's ability to control the precise amount of delivered insulin will be diminished.